Digital data is stored on tape cartridges that include a magnetic tape media wound between a pair of tape reels as data is transferred to or from the media. The physical space required to store data on tape cartridges is an important concern. To conserve space, tape handling devices often use a single reel cartridge design, which utilizes a tape reel located within a removable tape cartridge and a tape reel located within the tape handling device.
According to this characterization, after a tape cartridge is inserted into the tape handling device, e.g., a tape drive, the tape media must be loaded into the drive from the cartridge. The loading operation includes connecting the tape media to the tape reel in the drive, typically referred to as a take-up reel, and winding the tape media to a start point or read/write position.
Various methods have been employed to perform this connection operation. One such method utilizes a leader connected to the tape media (“tape cartridge leader”) that is designed to connect, e.g., via a buckle connection, to a leader connected to the take-up reel (“take-up leader”). After connection, the buckled leaders are wound through a tape path and around the take-up reel until the beginning of the tape media is in a read/write position relative to a tape head. It will be appreciated, that such operation requires a method for identifying, in the drive, the beginning of the tape media. One such method to identify the beginning of the tape media is a beginning of tape (BOT) aperture or hole. BOT apertures are formed in the beginning of the tape media, typically by the tape cartridge manufacturer, and are detectable by the drive to identify the same to the drive. Similarly, an end of tape (EOT) aperture may be included proximate the end of the tape media to identify the end of the tape to the drive.
Presently, there are numerous commercially available tape cartridges having various different formats or characteristics, such as tape thickness, track pitch, maximum recording densities, coercivity, etc. As the number of tape cartridge formats increases, format detection is of increasing importance, both to protect tape cartridges from damage, as well as to protect tape drives from damage, due to incompatibility.
One conventional approach to prevent incompatibility problems is to provide a feature or “key” on the cartridge housing that only permits insertion of the cartridge into one particular drive type, and prevents insertion of the cartridge into other drive types. Unfortunately, this presents special design challenges during the development of new drive and cartridge formats. Consider the case where a manufacturer desires to build a new drive compatible both with a new cartridge and an existing cartridge that includes a compatibility key. If the old cartridge is compatible with both the new and current drives, but the new cartridge is only compatible with the new drive, the new cartridge must have a feature to prevent use in the current drive, while the new drive must be designed to accommodate both the current and new compatibility features.
Another solution to the above problem is to provide a tape type hole in the tape media to identify a cartridge type to a drive. Unfortunately, however, to identify more than a few tape cartridge types, requires the use of multiple holes along an interval of the media, thereby utilizing areas of the media that would otherwise be usable for data storage. A related problem with the provisioning of one or more holes in the tape media is localized weakening of the tape structurally, leaving it susceptible to stretching or tearing. Still another problem with the provisioning of holes, is that pressure generated by the winding of the successive layers of tape can result in an imprint in adjacent portions of the tape. These imprints result in track distortion and can cause portions of the tape to become unreadable by the drive. In particular, imprints create a gap between the tape media and the tape head during reading, such that the head is unable to read from the imprinted area.
Yet another problem with provisioning holes in tape media is debris generated during spooling of the media through the tape path. In this case, the holes provide a non-uniform point of contact between the media and components of the tape path (e.g., the tape head) that can cause portions of the media to “flake” off in the region of the hole, resulting in debris within the tape handling device and a weakened area on the tape media. Such debris is highly undesirable as it may affect the operation of other components including the tracking of the media through the tape path. Yet another problem with provisioning of holes in the tape media is related to the desirability of producing tape media in a thinner form factor. Such media is more susceptible to the above-described problems of damage and debris.